1. Field of the invention
This invention relates to automatic one-way clutch means for use in an incrementing mechanism having a driving member rotatably and slidably mounted within a tubular body and arranged to advance an elongate element in one direction with respect to the tubular body within which the element also is mounted. In addition, in its preferred aspects this invention further relates to such an incrementing mechanism adapted for use in conjunction with an injector device to permit the accurate dispensing of a required pre-set dose of a medicament, whenever the device is used. The invention further relates to an injector device per se.
2. Related Art
In my EP-0673482-A, I have described and claimed an incrementing mechanism primarily intended for use with a hypodermic syringe, to permit the setting of a required dose of a medicament, such as insulin, whereafter the depression of plunger accurately dispenses the required dose through a needle connected to the syringe. The entire disclosure of the specification of EP-0673482 is incorporated herein by this reference thereto, and reference may be made thereto (or WO 94/15120, on which EP-0673482 is based) for a further description of the prior art mechanism.
Tests on and trials of the mechanisms described in EP-0673482 have lead to further development of those mechanisms to give improved operating performance, greater reliability and dose dispensing accuracy. It has also been possible to simplify the manufacture of the mechanisms and hence reduce the manufacturing costs, without compromising performance. Further development has resulted in three distinct versions of injector device incorporating the mechanisms—namely: (1) a disposable injector which is discarded when a cartridge containing the medicament has been exhausted; (2) a reusable injector which can be reset when a cartridge containing the medicament has been exhausted, so permitting the replacement of the spent cartridge by a new one; and (3) a repeatable pre-set dose injector which permits the initial setting of a required dose and thereafter can be used solely for the repeated dispensing of just that dose. All of these versions incorporate the improved automatic one-way clutch means of this invention, for the incrementing mechanism forming the basis of the injector.